class DemoTest{

 private String name="123";

 public getName(){

  system.out.println("public getName " + name);

  return name;

 }

 private getName2(){

  system.out.println("private getName2 " + name);

  return name;

 }

}

class<DemoTest> calzz=DemoTest.class;

Constructor cons=clazz.getConstructor(new class[]{});//这个是得到class对象的构造方法。参数为构造方法的参数的类的对象。

DemoTest test=(DemoTest)cons.newInstance(new Object[]{});//生成相应的对象。参数new Object[]{} 就是构造方法对应的参数的具体值。如刚才的：

DemoTest test=(DemoTest)cons.newInstance(new Object[]{“李车”,"张三"});

Method method=clazz.getMethod("getName",new Class[]{String.class});

method.invoke(test,new Object[]{"王五"});

Field field=clazz.getDeclaredField("name");

field.setAccessible(true);

field.set("name","王五");

Method method=clazz.getDeclaredMethod("getName2");

method.setAccessible(true);

method.invoke(test,new Object[]{"王五"});